Several different embodiments of light emitting probes for administering photodynamic therapy (PDT) to an internal site within a patient's body are disclosed in commonly assigned U.S. Pat. No. 5,445,608. Further, a number of embodiments of flexible light emitting probes are disclosed in commonly assigned pending U.S. patent application Ser. No. 08/613,390 and a continuation-in-part patent application thereof, Ser. No. 08/633,171, both entitled, "Flexible Microcircuits for Internal Light Therapy." In the above-referenced patent, it is generally contemplated that a probe containing a plurality of light sources can be transcutaneously introduced to a desired treatment site through a surgical incision and then left in place for an extended period of time so that the light emitted by light emitting diodes (LEDs) or other types of light sources included in the probe can effect PDT to destroy abnormal tissue or other types of pathogenic organisms that have absorbed a photodynamic agent. Similarly, the flexible microcircuits of the above-noted pending patent applications are generally intended to be introduced into the body through a natural opening or through a small incision and positioned at the treatment site using conventional endoscopic techniques. These applications teach that a probe may be fixed at a treatment site using sutures, staples, or a biocompatible adhesive.
While any of the techniques that are typically used for attaching a medical device to a site within a patient's body can effectively anchor a rigid or flexible light emitting probe in a desired position, additional time and steps are required for a surgeon to endoscopically affix the device in place after it has been positioned at a treatment site. Even if the treatment site is fully exposed through a surgical procedure, it will typically be necessary to attach the probe at the treatment site before closing the incision. Clearly, it would be desirable to use a mechanism that is selectively deployed from outside the patient's body to fix a probe at a treatment site, without requiring the physician to use sutures, staples, or adhesive.
U.S. Pat. No. 5,267,960 (Hayman et al.) discloses a "Tissue Engaging Catheter for a Radioactive Source Wire," which teaches a selectively deployed anchor comprising two spring loaded, hook-shaped arms positioned at a distal end of a catheter. The catheter is inserted and moved to a desired location within a patient's body; the arms are then slidably advanced distally from within the tubular body of the catheter. Since the ends of the arms are disposed inside the tubular body as it is inserted into the desired location, they are prevented from engaging adjacent tissue. However, when slid outside the tubular body of the catheter, the tips of the arms penetrate slightly into the tissue, anchoring the distal end of the catheter in place. When thus selectively deployed, one of the arms may extend forward and one backward to prevent movement of the catheter in either longitudinal direction, or both arms may extend generally in the same direction. The arms are made of a biologically inert material such as stainless steel. To detach the ends of the arms from the tissue, the outer tubular body of the catheter can be advanced, forcing the arms to slide back inside the tubular structure. The reference also teaches that the structure or plug to which the arms are attached can be rotated about its longitudinal axis to unthread the plug from the inner member of the catheter so that the catheter can be withdrawn from the patient's body, leaving the plug in place. Once the catheter is anchored, a radioactive wire implant can be advanced through the interior of the catheter to provide treatment to the site at which the distal end of the catheter is fixed.
Although U.S. Pat. No. 5,267,960 describes how the hooked arms can be disengaged from the tissue, the technique requires the manual manipulation of the catheter relative to the inner tubing to which the hooked arms are coupled. If the treatment site is disposed in an organ having tissue that is very frangible, such as the liver, it is possible that the mechanical disengagement of the hooked arms will cause damage to the tissue at the site where the fixture was deployed. In addition, the technique disclosed in the above-referenced patent for anchoring the distal end of a catheter to a site is not particularly applicable to attaching a light source probe comprising a sheet on which an array of light sources are deployed to a tissue surface at a treatment site, since once the sheet is deployed, it will likely not be practical to engage or disengage hooks on the sheet in the manner disclosed in the prior art patent reference. Thus, another approach that enables almost any type of medical device to be selectively engaged and disengaged from tissue at a treatment site is required to minimize the time and effort required to affix such a device in place, and then subsequently remove the device from the patient's body.